Rotational drag has very little effect

I have a rectangular body 80x80 with mass 1 spinning at an angular velocity of 4. Even if I set the RotationalDragCoefficient as high as 1, there is no visible reduction in velocity. In 5 seconds, the body's angular velocity reduced to 3.93. With a RotationalDragCoefficient
of 10, the velocity reduced to 3.4 in 5 seconds. Is this expected? Given that the default rotational drag is 0.001, I would've thought that multiplying it by 1000 or 10000 would be more that enough to get a significant effect.